Topic: CB750 "R1" camshaft

[lwitchey]

I picked up this box of CB750 parts and in it I found this cam. It is clearly stamped R1 and is in good shape. I was wondering if anyone knew what bike this is off of, or what the specs. are of it. I have a few motor parts and I am planning on building a motor.

[MCRider]

DING DING DING you are the winner!

You have a very early (earliest) cam from a 1969 CB750. This is the hottest of all stock cams, with the 8500 redline and several horsepower more than later versions. Can be used with stock springs and all other stock parts, but is noticabley healthier.

I have an R3 (pretty good) and an R10 (wimpy, wimpy).

If you were building a stock production racer that is the cam you would want. Even if an 836cc that cam will give great performance thru the stock rpm range.

Honda stopped selling each older cam as the new ones were introduced, so that cam is not available anymore.

[bucky katt]

wow, glad i didnt sell the 2 i got in my box-o-parts

[KB02]

Are going to be for sale now?  $ $

I know that's how my mind works anyway. 

[MCRider]

Are going to be for sale now?  $ $

I know that's how my mind works anyway. 

I've sold several R10s for $35. I wouldn't sell an R3 or earlier for less than $150. If you found a restorer who really needed it, well.... Hmmm sandcast?

Lots of other people wouldn't care, so its a personal thing.

[bucky katt]

i likely will sell one of them.

[ColinMc]

Can you see the stamping on what cam you have just with the valve cover off? Or does the cam have to be removed to tell? I have a few CB750 motors and would be curious to see what they have...

[754]

Does anyone know if they are hotter than 78 F cam? They are  noticeably different even ar first glance.

 I have a NOS 750 cam, but I think it is a  r7

[MCRider]

Can you see the stamping on what cam you have just with the valve cover off? Or does the cam have to be removed to tell? I have a few CB750 motors and would be curious to see what they have...

Gotta take the valve cover off, that's all. The stamp is on the open area between the sprocket and the first set of lobes.
Rotate it till it comes up.

[MCRider]

Does anyone know if they are hotter than 78 F cam? They are  noticeably different even ar first glance.

 I have a NOS 750 cam, but I think it is a  r7

Don't know.

R7 would be an in between (duh) maybe K3 vintage.

[Sam Green Racing]

I picked up this box of CB750 parts and in it I found this cam. It is clearly stamped R1 and is in good shape. I was wondering if anyone knew what bike this is off of, or what the specs. are of it. I have a few motor parts and I am planning on building a motor.

These guys are talking a load off crap, that cam is a load of rubbish, send it to me for dissposal

Sam.

[ColinMc]

Can you see the stamping on what cam you have just with the valve cover off? Or does the cam have to be removed to tell? I have a few CB750 motors and would be curious to see what they have...

Gotta take the valve cover off, that's all. The stamp is on the open area between the sprocket and the first set of lobes.
Rotate it till it comes up.

Sweet! I know what i'm doing later tonight lol

[Sam Green Racing]

Diggin fer gold

[Don R]

Popped the cover of my stuck K0 motor, dang, R9. somebody got in there already there's an allen head bolt in one of the cam tower holes. the ones that usually strip. No gold here, the broken 812 engine had an R3.

[Spanner 1]

Just looked at my opened K8 motor and it's an R2..!!!, WTHeck.....how's that possible ?...I'm 99.9% sure that motor was never open before, all the screws/bolts were factory 'virgin' and only 16K on the motor ?

[lwitchey]

Wow! I am happy to hear that. The bad thing is I had another R1 that came in the same box that was in a head that I sold on E bay for $35.00. Now that I know that it is of value, I am not sure that I want to use it.

[MCRider]

Just looked at my opened K8 motor and it's an R2..!!!, WTHeck.....how's that possible ?...I'm 99.9% sure that motor was never open before, all the screws/bolts were factory 'virgin' and only 16K on the motor ?

I can't explain it, and I reserve the right to be completely wrong about the "R" thing. But I have no evidence to say I'm off base.

I have visually compared many cams over the years and the differences are easily seen with the naked eye, and progress linearly from early to late.

Curious.

[bryanj]

I'm willing to be stot down in flames but i thought the "R" number was just a casting mark and bore no relation to the age or profile

[mystic_1]

Lacking solid source data, the only way to find out would be for a bunch of people to measure their cams and compare results.

mystic_1

[MCRider]

I'm willing to be stot down in flames but i thought the "R" number was just a casting mark and bore no relation to the age or profile

That could be, my source was a couple of Honda mechanics back in my youth, and then my personal observation. Probably seen 20 cams over time and they seemed to progress as mentioned.

However, as mentioned, I would bet I'm right, but I wouldn't bet the farm.  

The guy with the R2 in a K8 throws a wrench in the works. Now if it were a R12, that would be perfect.

[MCRider]

Let me rephrase my posts to reduce the certainty of my idea on this subject.

In the meantime if Spanner1 gets a chance to measure his lobes on the R2, we can compare. I checked my inventory and I have an R2, R3, and R10. I cannot confirm what K series these came from that info was lost long ago. I can say that they are visibly different from each otehr R2 having more lift and duration, assuming the base circles are the same.

I'll do some comparos this weekend when I'm in the shop.

In the meantime I'll dwell in my delusion as it sounds cool    but I'll say no more.

[nobody]

I should crack open my spare engine and see what I have in there. It's got the allen head bolts on it so maybe I'll get lucky and find some gold.

This raises a question though. How much detuning was there over time? I know the 78f was supposed to be a faster bike (even with it's valve guide issues) but all this detuning talk has me wondering. How will it match up to my stock 74k? Will the 78f blow it out of the water or am I in for a suprise when I finally get it going and realize it's barely faster than the 74? Or maybe even slower...?

[MCRider]

I should crack open my spare engine and see what I have in there. It's got the allen head bolts on it so maybe I'll get lucky and find some gold.

This raises a question though. How much detuning was there over time? I know the 78f was supposed to be a faster bike (even with it's valve guide issues) but all this detuning talk has me wondering. How will it match up to my stock 74k? Will the 78f blow it out of the water or am I in for a suprise when I finally get it going and realize it's barely faster than the 74? Or maybe even slower...?

The Ks were significantly downtuned at least until K7, but i think it and K8 were not immune. Reduction of 6 to 8 horsepower, but HondaMan would know for sure. It wasn't all the cam, but a lot of it was.

The Last 2 models of the F were much faster, but only slightly more so than the first K.

That's my understanding. Your 78F should surpass your 74K easily. Assuming they are both running up to par etc.

And again, I'll classify this as something I think i know, not something I know I know.

[nobody]

Haha, well you've been plenty helpful thus far so I'll take your word on it.

[MCRider]

Haha, well you've been plenty helpful thus far so I'll take your word on it.

According to one of the CB750 books i have, the Fs with the head/valve angle change (77/78?) were pepped up to compete with the DOHC suzis, etc while waiting on the Honda DOHC.  The Ks were left as they were for the Windjammer Fairing crowd.